In electronics, an optocoupler, also referred to as an opto-isolator, photocoupler, or optical isolator, is an optoelectronic device designed to transfer electrical signals by utilizing light waves to provide coupling with electrical isolation between its input and output. One goal of an optocoupler is to prevent high voltages or rapidly changing voltages on one side of the circuit from damaging components or distorting transmissions on the other side.
A typical optocoupler includes a light source, such as a Light Emitting Diode (LED), a photodetector, and an insulation medium. As the name suggests, an optical path needs to be created between the LED and photodetector via the insulation medium. This is traditionally done by using an optically-transparent material such as silicone to create the light path. The insulation medium not only acts to allow the transmission of light from the LED to the photodetector, but the insulation medium also electrically insulates the input and output sides of the circuit.